Answer:
20.2 %
Step-by-step explanation:
A typical high-income household in 1980 earned $140,397.
A similar household in 2009 earned $168,727.
We need to find the relative increase in income for these households from 1980 to 2009.
It can be calculated as follows :
[tex]\%=\dfrac{168727-140397}{140397}\times 100\\\\=20.17\%\\\\=20.2\%[/tex]
So, the required percent is 20.2%.